Image projection apparatus

ABSTRACT

An image projection apparatus includes a light source; an intake port to take in low-temperature air into the image projection apparatus; an exhaust port to exhaust air from the image projection apparatus; a ventilation unit to generate an air flow from the intake port to the exhaust port; a first flow path for hot-air exhaust having increased its temperature by taking heat from the light source; a second flow path for a part of the low-temperature air, taken from the intake port; and a mixing unit to mix the hot-air exhaust flowing from the first flow path and the low-temperature air flowing from the second flow path. The air mixed and exhausted from the mixing unit converges with another part of the low-temperature air, flowing from a third flow path set outside the mixing unit, at a space between the mixing unit and the exhaust port.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority pursuant to 35 U.S.C. §119 to JapanesePatent Application No. 2012-062083, filed on Mar. 19, 2012 in the JapanPatent Office, the disclosure of which is incorporated by referenceherein in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to an image projection apparatus.

2. Background Art

Image projection apparatuses such as projectors receive image data frompersonal computers or video cameras to project an image using an imageprojector. The image projector projects and displays the image onto ascreen using light emitted from a light source.

The light source of the image projection apparatus may be a halogenlamp, a metal-halide lamp, or a high-pressure mercury vapor lamp, all ofwhich generate heat when they emit light. Therefore, a ventilation unitsuch as a blower or a fan is used to cool the light source. The air usedfor cooling the light source is itself heated by the light source and isthen exhausted as hot exhaust from an exhaust unit such as an exhaustport. This hot-air exhaust can reach uncomfortably high temperatures.

JP-2008-292832-A and JP-2910742-B (or JP-H11-87963-A) disclose imageprojection apparatuses having a mixing unit that mixes the hot-airexhaust with cool air to decrease the temperature of the hot-airexhaust, and then such mixed air is exhausted from the exhaust port.

However, this approach cannot lower the temperature of the exhaust toacceptable levels because the hot-air exhaust and cool air are mixedonly once.

SUMMARY

As one aspect of the present invention, an image projection apparatus isdevised. The image projection apparatus includes a light source to emitlight for projecting an image to be projected; an intake port to take inlow-temperature air into the image projection apparatus; an exhaust portto exhaust air from the image projection apparatus; a ventilation unitto generate an air flow from the intake port to the exhaust port; afirst flow path for hot-air exhaust having increased its temperature bytaking heat from the light source while flowing around the light source;a second flow path for a part of the low-temperature air, taken from theintake port, having a temperature lower than the hot-air exhaust; and amixing unit to mix the hot-air exhaust flowing from the first flow pathand the low-temperature air flowing from the second flow path. The airmixed and exhausted from the mixing unit converges with another part ofthe low-temperature air taken from the intake port, flowing from a thirdflow path set outside the mixing unit, at a space between the mixingunit and the exhaust port.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages and features thereof can be readily obtained and understoodfrom the following detailed description with reference to theaccompanying drawings, wherein:

FIG. 1 shows a perspective view of a projector according to an exampleembodiment and a projection plane;

FIG. 2 shows a pattern of light paths from a projector to a projectionplane;

FIG. 3 shows a schematic perspective view of a projector;

FIG. 4 shows a perspective view of a main unit of a projector;

FIG. 5 shows a perspective view of an image generation unit;

FIG. 6 shows a schematic perspective view of a light source unit;

FIG. 7 shows a perspective view of an image generation unit and alighting unit;

FIG. 8 shows a perspective view of the image generation unit of FIG. 7;

FIG. 9 shows a perspective view of a first optical unit with thelighting unit and the image generation unit;

FIG. 10 shows a cross-sectional view along a line D-D of FIG. 9;

FIG. 11 shows a perspective view of a second optical unit configuredwith a projection lens unit, the lighting unit, and the image generationunit;

FIG. 12 shows a perspective view of the second optical unit configuredwith the first optical unit, the lighting unit, and the image generationunit;

FIG. 13 shows a schematic view of the light path from the first opticalsystem to a projection plane;

FIG. 14 schematically shows a layout of units in the projector;

FIG. 15 shows an example of use environment of the projector accordingto an example embodiment;

FIG. 16 shows an example of use environment of a conventional projector;

FIG. 17 shows another example of use environment of a conventionalprojector;

FIG. 18 shows a perspective view of the projector viewed from a bottomface of the projector;

FIG. 19 shows a perspective view of the projector when an openablyclosable cover is removed from the projector;

FIG. 20 shows a schematic view of airflow patterns in the projector;

FIG. 21 shows a perspective view of a mixing duct and a light sourcehousing;

FIG. 22 shows a cross-sectional view of FIG. 21;

FIG. 23 shows a mixing duct provided with a plurality of plate members;

FIG. 24 shows a schematic perspective view of a mixing duct according toa variant example embodiment;

FIG. 25 shows a cross-sectional view of the mixing duct of FIG. 24; and

FIG. 26 shows an inclining member having a step-like shape.

The accompanying drawings are intended to depict exemplary embodimentsof the present invention and should not be interpreted to limit thescope thereof. The accompanying drawings are not to be considered asdrawn to scale unless explicitly noted, and identical or similarreference numerals designate identical or similar components throughoutthe several views.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A description is now given of exemplary embodiments of the presentinvention. It should be noted that although such terms as first, second,etc. may be used herein to describe various elements, components,regions, layers and/or sections, it should be understood that suchelements, components, regions, layers and/or sections are not limitedthereby because such terms are relative, that is, used only todistinguish one element, component, region, layer or section fromanother region, layer or section. Thus, for example, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the present invention.

In addition, it should be noted that the terminology used herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of the present invention. Thus, for example, asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. Moreover, the terms “includes” and/or “including”, when usedin this specification, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Furthermore, although in describing views shown in the drawings,specific terminology is employed for the sake of clarity, the presentdisclosure is not limited to the specific terminology so selected and itis to be understood that each specific element includes all technicalequivalents that have the same function, operate in a similar manner,and achieve a similar result. Referring now to the drawings, anapparatus or system for an image projection apparatus such as aprojector according to an example embodiment is described hereinafter.

FIG. 1 shows a perspective view of a projector 1 and a projection plane101. The projector 1 includes, for example, a transparent glass 51, anoperation unit 83, and a focus lever 33. As shown in FIG. 1, theprojector 1 has the transparent glass 51 on its top face, from which aprojection image P is projected to the projection plane 101. Theprojection image P projected from the transparent glass 51 is displayedon the projection plane 101 such as a screen. Further, the projector 1has the operation unit 83 on its top face, by which a user can operatethe projector 1. Further, the projector 1 has the focus lever 33 on itsside face for adjusting the focus of image. Hereinafter, the normal linedirection of the projection plane 101 is set as X direction, the shortside direction of the projection plane 101 (or top/bottom direction) isset as Y direction, and the long side direction of the projection plane101 (or horizontal direction) is set as Z direction.

FIG. 2 shows a pattern of light paths from the projector 1 to theprojection plane 101. The projector 1 includes, for example, a lightsource unit having a light source, and an image generator A to generateimages using the light emitted from the light source. The imagegenerator A includes, for example, an image generation unit 10, and alighting unit 20. The projector 1 further includes a projection opticalsystem B.

The image generation unit 10 includes an image generation element suchas a digital mirror device (DMD) 12. The lighting unit 20 reflects andradiates light coming from the light source to the DMD 12 to generate alight image. The projection optical system B projects the light image onthe projection plane 101. The projection optical system B includes aleast one pass-through type reflection optical system. For example, theprojection optical system B includes a first optical unit 30, and asecond optical unit 40.

The first optical unit 30 includes, for example, a first optical system70 of co-axial system having the positive power. The second optical unit40 includes, for example, a reflection mirror 41, and a curved mirror 42having the positive power.

The DMD 12 can generate an image using the light emitted from the lightsource. Specifically, the light emitted from the light source irradiatesthe DMD 12 and an image is generated by modulating the light irradiatedby the lighting unit 20. The image generated by the DMD 12 is projectedonto the projection plane 101 via the first optical system 70 of thefirst optical unit 30, and the reflection mirror 41 and the curvedmirror 42 of the second optical unit 40.

FIG. 3 shows a schematic perspective view of an internal configurationof the projector 1. As shown in FIG. 3, the image generation unit 10,the lighting unit 20, the first optical unit 30, the second optical unit40 are arranged along the Y direction in FIG. 3 parallel to theprojection plane 101. Further, a light source unit 60 can be disposed ata right side of the lighting unit 20 in FIG. 3.

Further, as shown in FIG. 3, the first optical unit 30 has a lens holder32 having legs 32 a 1 and 32 a 2, and the image generation unit 10 hasscrew stoppers 262 used to fix the image generation unit 10 to thelighting unit 20 using screws.

A description is given of the configuration of each unit. Initially, thelight source unit 60 is described. FIG. 4 shows a schematic perspectiveview of the light source unit 60. The light source unit 60 includes alight-source bracket 62, and a light source 61 fixed on the light-sourcebracket 62. The light source 61 is, for example, a halogen lamp, ametal-halide lamp, and a high-pressure mercury vapor lamp. Further, thelight-source bracket 62 has a connector 62 a connectable to apower-source connector of a power source unit 80 (see FIG. 14).

Further, a holder 64 is fixed on the light exiting side of the lightsource 61 disposed on the light-source bracket 62 by using screws,wherein the holder 64 retains a reflector or the like. Further, a lightexiting window 63 is disposed for the holder 64 while the light exitingwindow 63 is disposed at a side opposite the position of the lightsource 61. The light emitted from the light source 61 can be guided tothe light exiting window 63 by the reflector retained in the holder 64,and exits from the light exiting window 63.

Further, light source position-setting members 64 a 1 to 64 a 3 aredisposed at the top face of the holder 64 and both ends of the Xdirection of the bottom face of the holder 64 so that the light sourceunit 60 can be positioned correctly on a lighting unit bracket 26 of thelighting unit 20 (FIG. 6). For example, the light sourceposition-setting member 64 a 3 disposed at the top face of the holder 64has a protruded-shape, and the light source position-setting members 64a 1 and 64 a 2 disposed at the bottom face of the holder 64 have a holeshape.

Further, a light-source air intake port 64 b is disposed at a side faceof the holder 64 to take in air used for cooling the light source 61,and a light-source air exhaust port 64 c is disposed at the top face ofthe holder 64 to exhaust air heated by the heat of the light source 61.

Further, a pass-through area 65 is disposed for the light-source bracket62 to take in air sucked in by an air-intake blower 91 (see FIG. 20) tobe described later. Further, an opening 65 a is disposed at anair-intake side of the pass-through area 65 as shown in FIG. 4 to send apart of airflow flowing into the pass-through area 65 to a space betweenthe light source unit 60 and an openably closable cover 54 (see FIG.18), to be described later. The cooling of the light source unit 60 willbe described later. The pass-through area 65 may be also referred to asthe duct 65.

Further, as shown in FIG. 4, the light source position-setting member 64a 3 having a protruded-shape is provided on a plane face portion 64 d 2disposed at the top face of the holder 64, and the light sourceposition-setting members 64 a 1 and 64 a 2 having the hole shape isdisposed at a plane face portion 64 d 1 of the bottom face of the holder64. Such plane face portion 64 d 2 and the plane face portion 64 d 1 canbe used as abutting members to be abutted to the lighting unit bracket26 when pressed by a pressing member of the openably closable cover 54to be described later.

A description is given of the lighting unit 20 with reference to FIG. 5,which shows a perspective view of optical parts encased in the lightingunit 20 and other units. As shown in FIG. 5, the lighting unit 20includes, for example, a color wheel 21, a light tunnel 22, two relaylenses 23, a cylinder mirror 24, a concave mirror 25, wherein such partscan be retained by the lighting unit bracket 26. The lighting unitbracket 26 includes, for example, a casing 261 that encases the relaylenses 23, the cylinder mirror 24, and the concave mirror 25. Among foursides of the casing 261, only one side has a side face (i.e., right sideof FIG. 5), and other three sides are opening. Further, an OFF plate 27(FIG. 6) is disposed at one opening-side of the X direction in FIG. 5,and a cover member is disposed at another opening-side of the Xdirection in FIG. 5. With such a configuration, the relay lenses 23, thecylinder minor 24, and the concave mirror 25 encased in the casing 261of the lighting unit bracket 26 can be covered by the lighting unitbracket 26, the OFF plate 27, and the cover member.

Further, a through-hole 26 d is disposed on the bottom face of thecasing 261 of the lighting unit bracket 26 so that the DMD 12 can beexposed through the through-hole 26 d.

Further, the lighting unit bracket 26 includes, for example, three legs29. Such legs 29 can contact a base member 53 (see FIGS. 13, 18, 19) ofthe projector 1 to support the weight of the first optical unit 30 andthe second optical unit 40 stacked and fixed on the lighting unitbracket 26. Further, by providing the legs 29, a space for taking inexternal air to a heat exchanger such as a heat sink 13 (FIG. 6) thatcools the DMD 12 of the image generation unit 10, can be arranged, to bedescribed later.

Further, as shown in FIG. 5, the lens holder 32 of the first opticalunit 30 includes, for example, legs 32 a 3 and 32 a 4, and the secondoptical unit 40 includes, for example, a screw stopper 45 a 3.

FIG. 6 shows a perspective view of the image generation unit 10, thelighting unit 20, and a projection lens unit 31 viewed from thedirection C shown in FIG. 5. The casing 261 of the lighting unit bracket26 has a top face 26 b extending in a direction perpendicular to the Ydirection of FIG. 6. Through-holes are disposed at four corners of thetop face 26 b to fasten the first optical unit 30 with screws byinserting the screws into the through-holes. For example, FIG. 6 showsthe through-holes 26 c 1 and 26 c 2.

Further, as shown in FIG. 6, position-setting holes 26 e 1 and 26 e 2are respectively disposed next to the through-holes 26 c 1 and 26 c 2 toset the first optical unit 30 at a correct position with the lightingunit 20. As for such position-setting holes 26 e 1 and 26 e 2, theposition-setting hole 26 e 1 disposed at the color wheel 21 side is usedas a primary position-setting hole having a circular hole shape, and theposition-setting hole 26 e 2 disposed at an opposite side of the colorwheel 21 is used as a secondary position-setting hole having a slot holeextending in the Z direction.

Further, a position-setting protrusion 26 f is disposed around each ofthe through-holes 26 c 1 and 26 c 2, wherein the position-settingprotrusion 26 f protrudes from the top face 26 b of the lighting unitbracket 26. The position-setting protrusion 26 f is used to set thefirst optical unit 30 at a correct position in the Y direction.

If the precision of positioning is to be enhanced in the Y directionwithout providing the position-setting protrusion 26 f, the flatness ofthe entire top face of the lighting unit bracket 26 is required to beenhanced, which is costly. By providing the position-setting protrusion26 f, the flatness is required to be enhanced only at theposition-setting protrusion 26 f. Therefore, the precision ofpositioning can be enhanced in the Y direction while reducing the cost.

Further, the top face of the lighting unit bracket 26 has an openingcovered by a light shield plate 262 engaging the lower end of theprojection lens unit 31, by which the intrusion of light from the upperside into the casing 261 can be prevented.

Further, the top face 26 b of the lighting unit bracket 26 has a cutoutbetween the through-holes 26 c 1 and 26 c 2 of the top face 26 b so thatthe second optical unit 40 can be screwed to the first optical unit 30easily, to be described later.

A light source positioning member 26 a 3 is disposed at one end of thelighting unit bracket 26 at the color wheel 21 side (Z direction in FIG.6). The light source positioning member 26 a 3 has a cylinder-like shapehaving a through-hole, to which the light source position-setting member64 a 3 having the protruded-shape (FIG. 4), disposed at the top face ofthe holder 64 of the light source unit 60, engages. Further, two lightsource positioning members 26 a 1 and 26 a 2 having protruded-shape aredisposed at a lower side of the light source positioning member 26 a 3,to which the light source position-setting member 64 a 1 and 64 a 2disposed on the holder 64 at the light-source bracket 62 side, which arethe through-holes, engage respectively. By respectively engaging thelight source position-setting members 64 a 1 to 64 a 3 disposed for theholder 64 to the light source positioning members 26 a 1 to 26 a 3disposed for the lighting unit bracket 26 of the lighting unit 20, thelight source unit 60 can be fixed at the correct position of thelighting unit 20 (FIG. 3).

Further, the lighting unit bracket 26 includes a lighting unit cover 28that covers the color wheel 21 and the light tunnel 22.

FIG. 7 shows a light path L of light in the lighting unit 20. The colorwheel 21 has a disc shape and is fixed on a motor shaft of a color motor21 a. The color wheel 21 includes, for example, R (red), G (green), andB (blue) filters along the rotation direction. The light focused by areflector disposed for the holder 64 of the light source unit 60 passesthrough the light exiting window 63, and then reaches the peripheralarea of the color wheel 21. The light that has reached the peripheralarea of the color wheel 21 is separated into R, G, B lights along thetimeline as the color wheel 21 rotates.

The lights separated by the color wheel 21 enter the light tunnel 22.The light tunnel 22 is a tube-shaped member having a square-like crossshape, and its internal face is finished as a minor face. The lightentered the light tunnel 22 reflects a plurality of times on theinternal face of the light tunnel 22, and is then emitted as uniformlight to the relay lenses 23.

The light that has passed the light tunnel 22 passes the two relaylenses 23, reflects on the cylinder mirror 24 and the concave mirror 25,and is then focused on an image generation face of the DMD 12 as animage.

A description is given of the image generation unit 10 with reference toFIG. 8, which shows a perspective view of the image generation unit 10.As shown in FIG. 8, the image generation unit 10 includes, for example,a DMD board 11 to which the DMD 12 is attached. The DMD 12 is attachedto a socket 11 a disposed on the DMD board 11 while orienting an imagegeneration face composed of micro mirrors arranged in a lattice patternto an upward direction. The DMD board 11 includes a drive circuit todrive micro mirrors.

A heat exchanger such as the heat sink 13 is fixed on a distal side ofthe DMD board 11 (i.e., a face opposite a face having the socket 11 a)to cool the DMD 12. The DMD board 11 has a through-hole area to whichthe DMD 12 is attached, and the heat sink 13 has a protruded portion 13a (FIG. 7) insertable into the through-hole area. The protruded portion13 a has an edge portion having a flat shape. By inserting the protrudedportion 13 a into the through-hole area, the flat edge portion of theprotruded portion 13 a can contact the distal side of the DMD 12 (i.e.,face opposite the image generation face). An elastic and flexible heatconduction sheet can be attached on the flat edge portion of theprotruded portion 13 a and/or an area of the distal side of the DMD 12so that the heat sink 13 and the distal side of the DMD 12 can beclosely contacted to enhance the thermal conductivity.

The heat sink 13 can be fixed on a face opposite a face disposed of thesocket 11 a of the DMD board 11 by applying pressure using a fixingdevice 14. The fixing device 14 includes, for example, a plate-likefixing part 14 a at a right distal side of the DMD board 11 (right sidein FIG. 8), and a plate-like fixing part 14 a at a left distal side ofthe DMD board 11 (left side in FIG. 8) disposed at as counterpartmembers with each other. As shown in FIG. 8, one end and other end ofthe plate-like fixing parts 14 a are linked by a pressure member 14 bextending in the Z direction in FIG. 8.

When the image generation unit 10 is fixed to the lighting unit bracket26 (FIG. 6) using screws, the heat sink 13 is pressed and fixed to theface opposite the face disposed of the socket 11 a of the DMD board 11by applying force from the fixing device 14.

A description is given of fixing of the lighting unit bracket 26 of theimage generation unit 10. Initially, the image generation unit 10 ispositioned with respect to the lighting unit bracket 26 so that the DMD12 can face the through-hole 26 d disposed on the bottom face of thelighting unit bracket 26 of the lighting unit 20 (FIG. 5). Then, a screwis inserted into each of through-holes disposed for the fixing part 14a, and each of through-holes 15 disposed for the DMD board 11 from alower side, and the screw is screwed into each of screw holes disposedat the bottom face of the screw stopper 262 (FIG. 3) of the lightingunit bracket 26 to fix the image generation unit 10 to the lighting unitbracket 26. Further, as the screw is screwed into the screw stopper 262disposed for the lighting unit bracket 26, the pressure member 14 bpresses the heat sink 13 toward the DMD board 11. With such aconfiguration, the heat sink 13 can be pressed and fixed on the faceopposite the face disposed with the socket 11 a of the DMD board 11 byusing the fixing device 14.

As such, the image generation unit 10 can be fixed to the lighting unitbracket 26, and the three legs 29 shown in FIG. 5 can support the weightof the image generation unit 10.

The image generation face of the DMD 12 is composed of a plurality ofmovable micro mirrors arranged in a lattice pattern. Each of micromirrors can incline the mirror face about a torsion shaft for a givenangle, and can be set with two conditions of “ON” and “OFF”. When themicro mirror is set “ON”, the light coming from the light source 61 isreflected toward the first optical system 70 (FIG. 2) as shown by anarrow L2 shown in FIG. 7. When the micro mirror is set “OFF”, the lightcoming from the light source 61 is reflected toward the OFF plate 27,retained on the side face of the lighting unit bracket 26 shown in FIG.6, as shown by an arrow L1 shown in FIG. 7. Therefore, by driving eachmirror independently, the light projection can be controlled for eachpixel of image data to generate an image.

The light reflected to the OFF plate 27 is absorbed as heat and then theOFF plate 27 is cooled by the airflow flowing outside of the OFF plate27.

A description is given of the first optical unit 30 with reference toFIG. 9, which shows a perspective view of the first optical unit 30 withthe lighting unit 20 and the image generation unit 10. As shown in FIG.9, the first optical unit 30 is disposed over the lighting unit 20, andincludes, for example, the projection lens unit 31, and the lens holder32. The projection lens unit 31 retains the first optical system 70(FIG. 2) composed of a plurality of lenses, and the lens holder 32retains the projection lens unit 31. The lens holder 32 is disposed withfour legs 32 a 1 to 32 a 4 extending toward the downside, wherein FIG. 9shows the legs 32 a 2 and 32 a 3. The leg 32 a 1 is shown in FIG. 3, andthe leg 32 a 4 is shown in FIG. 5. Each of the legs 32 a 1 to 32 a 4 isformed of a screw hole on its bottom face to be used when fixed with thelighting unit bracket 26 using a screw.

Further, the projection lens unit 31 is disposed with a focus gear 36meshed with an idler gear 35. The idler gear 35 is meshed with a levergear 34, and the focus lever 33 is fixed to a rotation shaft of thelever gear 34. As shown in FIG. 1, the end of the focus lever 33 isexposed outside of the projector 1.

When the focus lever 33 is operated, the focus gear 36 is rotated viathe lever gear 34 and the idler gear 35. When the focus gear 36 isrotated, each of the plurality of lenses composing the first opticalsystem 70 disposed in the projection lens unit 31 can be moved to agiven direction to adjust a focus point of a projection image.

Further, the lens holder 32 includes, for example, four threadedthrough-holes 32 c 1 to 32 c 3 so that the second optical unit 40 can befixed with the first optical unit 30 using screws, in which a screw 48is screwed into each of the threaded through-holes 32 c 1 to 32 c 3.FIG. 9 shows three threaded through-holes 32 c 1 to 32 c 3, and thescrew 48 is inserted into each of the threaded through-holes 32 c 1 to32 c 3. In FIG. 9, the end of the screw 48 is shown. Further,positioning protruded members 32 d 1 to 32 d 3 are respectively formedaround each of the threaded through-holes 32 c 1 to 32 c 3, in whicheach of the positioning protruded members 32 d 1 to 32 d 3 protrudesfrom the face of the lens holder 32. FIG. 9 shows the positioningprotruded members 32 d 1 to 32 d 3.

FIG. 10 shows a cross-sectional view along a line D-D of FIG. 9. Asshown in FIG. 10, each of the legs 32 a 1 and 32 a 2 is disposed withpositioning protruded members 32 b 1 and 32 b 2, respectively. Thepositioning protruded member 32 b 1 (right side in FIG. 10) is insertedin the position-setting hole 26 e 1 having the circular hole shape,which is the primary position-setting hole disposed on the top face 26 bof the lighting unit bracket 26. The positioning protruded member 32 b 2(left side in FIG. 10) is inserted in the position-setting hole 26 e 2having the slot hole shape, which is the secondary position-settinghole. With such a configuration, the position in the Z direction and Xdirection can be set correctly.

Further, a screw 37 is inserted into each of the through-holes 26 c 1 to26 c 4 disposed for the top face 26 b of the lighting unit bracket 26,and then screwed into screw holes of each of the legs 32 a 1 to 32 a 4of the lens holder 32, by which the first optical unit 30 can be fixedto the lighting unit 20 with a correct position.

The second optical unit 40 includes a mirror holder 45 (see FIG. 12)that covers a portion of the projection lens unit 31 above the lensholder 32 to be described later. Further, as shown in FIG. 3, a spacebetween a part of the lens holder 32, lower than a part of the lensholder 32 corresponding to the projection lens unit 31 and the top face26 b of the lighting unit bracket 26 of the lighting unit 20 is exposedoutside. However, because the projection lens unit 31 engages the lensholder 32, the light does not enter the light path of projection lightfrom such exposed part.

A description is given of the second optical unit 40 with reference toFIG. 11 and FIG. 12. FIG. 11 shows a perspective view of the secondoptical unit 40 used as a second optical system configured with theprojection lens unit 31, the lighting unit 20, and the image generationunit 10. As shown in FIG. 11, the second optical unit 40 includes, forexample, the reflection mirror 41, and the curved mirror 42 having theconcave shape. The reflection face of the curved mirror 42 can befinished as a circular face, a rotation symmetrical non-circular face, afree curve shape, or the like.

FIG. 12 shows a perspective view of the second optical unit 40 with thefirst optical unit 30, the lighting unit 20, and the image generationunit 10. The second optical unit 40 passes the light reflected from thecurved mirror 42, and includes the transparent glass 51 to preventintrusion of dust to optical parts in the projector 1.

The second optical unit 40 includes, for example, a mirror bracket 43, afree mirror bracket 44, and a mirror holder 45. The mirror bracket 43retains the reflection mirror 41 and the transparent glass 51. The freemirror bracket 44 retains the curved mirror 42. The mirror holder 45holds the mirror bracket 43 and the free mirror bracket 44.

The mirror holder 45 has a box-like shape while the upper side, lowerside, and one side such as right side in the X direction in FIG. 12 areopened, and thereby the mirror holder 45 has a U-like shape when viewedfrom the top. The upper part of the mirror holder 45 includes aninclined portion extending along a direction set between the middle ofthe X and Y directions by increasing the height, and includes a parallelface parallel to the X direction. The inclined portion is disposed at aproximal side of the parallel face in the X direction. Further, theperipheral side of upper opening of the mirror holder 45 disposed at aproximal side in the X direction and extending in the Z direction isparallel to the Z direction in FIG. 12.

The mirror bracket 43 is attached to the upper part of the mirror holder45. The mirror bracket 43 includes an inclined side 43 a and ahorizontal side 43 b. The inclined side 43 a rises along a direction setbetween the middle of the X and Y directions by increasing the height asshown in FIG. 12. The horizontal side 43 b extends in a directionparallel to the X direction in FIG. 12. The inclined side 43 a contactsthe peripherals of the inclined portion of the mirror holder 45, and thehorizontal side 43 b contacts the peripherals of the horizontal part ofthe mirror holder 45, which is the top of the mirror holder 45. Theinclined side 43 a includes an opening, and the reflection mirror 41 isretained to cover the opening of the inclined side 43 a. The horizontalside 43 b includes an opening, and the transparent glass 51 is retainedto cover the opening of the horizontal side 43 b.

Each end of the reflection mirror 41 in the Z direction is pressed tothe inclined side 43 a of the mirror bracket 43 by the mirror pressingmember 46 such as a leaf spring to hold the reflection mirror 41 at theinclined side 43 a of the mirror bracket 43. For example, as shown inFIG. 12, one end of the reflection mirror 41 in the Z direction is fixedby the two mirror pressing members 46, and other end of the reflectionmirror 41 in the Z direction is fixed by the one mirror pressing member46.

Each end of the transparent glass 51 in the Z direction is pressed tothe horizontal side 43 b of the mirror bracket 43 by a glass pressingmember 47 such as a leaf spring to hold the transparent glass 51 on themirror bracket 43. Each end of the transparent glass 51 in the Zdirection is retained by using one glass pressing member 47 at each endin the Z direction.

The free mirror bracket 44 to retain the curved mirror 42 includes anarm portion 44 a at each side of the free mirror bracket 44, in whichthe arm portion 44 a extends and inclines along a direction set betweenthe middle of the X and Y directions as shown in FIG. 12. Further, thefree mirror bracket 44 includes a link portion 44 b that links such twoarm portions 44 a at the upper portion of the arm portions 44 a. The armportion 44 a of the free mirror bracket 44 is attached to the mirrorholder 45 so that the curved mirror 42 covers an opening of the mirrorholder 45.

The curved mirror 42 pressed toward the link portion 44 b of the freemirror bracket 44 by a free mirror pressing member 49 such as a leafspring at a substantially center of one end side of the transparentglass 51. Further, each end side of the first optical system 70 in the Zdirection in FIG. 12 is fixed to the arm portion 44 a of the free mirrorbracket 44 using a screw.

The second optical unit 40 is stacked and fixed on the lens holder 32 ofthe first optical unit 30. Specifically, the bottom side of the mirrorholder 45 has a bottom face 451 that faces an upper face of the lensholder 32. The bottom face 451 has three screw stoppers 45 a 1 to 45 a 3having tube-like shape, which can be fixed with the first optical unit30 by screws. FIG. 12 shows the screw stoppers 45 a 1 and 45 a 2, andFIG. 5 shows the screw stopper 45 a 3. The second optical unit 40 isfixed to the first optical unit 30 using screws, in which the screw 48is inserted into each of the threaded through-holes 32 c 1 to 32 c 3provided for the lens holder 32 of the first optical unit 30, andscrewed into each of the screw stoppers 45 a 1 to 45 a 3 to fix thesecond optical unit 40 to the first optical unit 30.

In such a configuration, the bottom face of the mirror holder 45 of thesecond optical unit 40 contacts the positioning protruded members 32 d 1to 32 d 3 of the lens holder 32, by which the second optical unit 40 canbe fixed at a correct position in Y direction.

As shown in FIG. 12, when the second optical unit 40 is stacked andfixed on the lens holder 32 of the first optical unit 30, a portion ofthe projection lens unit 31 that is above the lens holder 32 is encasedin the mirror holder 45 of the second optical unit 40. Further, when thesecond optical unit 40 is stacked and fixed on the lens holder 32, aspace is set between the curved mirror 42 and the lens holder 32, andthe idler gear 35 (FIG. 9) may be set in such space.

FIG. 13 shows a schematic view of the light path from the first opticalsystem 70 to the projection plane 101 such as a screen. The light fluxthat has passed through the projection lens unit 31 configuring thefirst optical system 70 is used to generate an intermediate imagebetween the reflection mirror 41 and the curved mirror 42, which is aconjugate image with respect to an image generated by the DMD 12. Suchintermediate image is generated as a curved image between the reflectionmirror 41 and the curved minor 42. Such intermediate image enters thecurved mirror 42 having a concave shape, and the curved mirror 42enlarges the intermediate image and projects the enlarged image onto theprojection plane 101.

As such, an optical projection system can be configured with the firstoptical system 70, and the second optical system. In such aconfiguration, the intermediate image is generated between the firstoptical system 70 and the curved mirror 42 of the second optical system,and the intermediate image is enlarged and projected by the curvedmirror 42, by which the projection distance to the screen can be setshorter. Therefore, the projector 1 can be used in small meeting roomsor the like.

Further, as shown in FIG. 13, the first optical unit 30 and the secondoptical unit 40 are stacked and fixed to the lighting unit bracket 26.Further, the image generation unit 10 is fixed to the lighting unitbracket 26. Therefore, the legs 29 of the lighting unit bracket 26 canbe fixed to the base member 53 while supporting the weight of the firstoptical unit 30, the second optical unit 40, and the image generationunit 10.

FIG. 14 schematically shows a layout of units in the projector 1. Asshown in FIG. 14, the image generation unit 10, the lighting unit 20,the first optical unit 30, and the second optical unit 40 are stackedalong the Y direction, which is the short side direction of theprojection plane 101. As shown in FIG. 14, the light source unit 60 isarranged in the Z direction with respect to other stacked units composedof the image generation unit 10, the lighting unit 20, the first opticalunit 30, and the second optical unit 40, which is the long sidedirection of the projection plane 101. As such, in an exampleembodiment, the image generation unit 10, the lighting unit 20, thefirst optical unit 30, the second optical unit 40, and the light sourceunit 60 can be arranged along the Y direction and Z directions, whichare parallel to a projection image and the projection plane 101.

Specifically, the projection optical system B having the first opticalunit 30 and the second optical unit 40 is stacked on the image generatorA having the image generation unit 10 and the lighting unit 20. Thelight source unit 60 is coupled to the image generator A in a directionperpendicular to the stacking direction of the image generator A and theprojection optical system B. Further, the image generator A and thelight source unit 60 can be arranged along a direction parallel to thebase member 53. Further, the image generator A and the projectionoptical system B may be arranged along a direction perpendicular to thebase member 53, in which the image generator A is disposed over the basemember 53, and then the projection optical system B is disposed over theimage generator A.

Further, as shown in FIG. 14, a power source unit 80 is stacked ordisposed above the light source unit 60, wherein the power source unit80 supplies power to the light source 61 and the DMD board 11. The lightsource unit 60, the power source unit 80, the image generator A, and theprojection optical system B are encased in a casing of the projector 1.The casing of the projector 1 includes the top face of the projector 1,the base member 53, and an outer cover 59 (see FIG. 18) used as the sideface of the projector 1 to be described later.

FIG. 15 shows an example of use environment of the projector 1 accordingto an example embodiment, and FIG. 16 and FIG. 17 show examples of useenvironment of conventional projectors 1A and 1B. As shown in FIG. 15 toFIG. 17, when the projector is used in a meeting room, the projector maybe placed on a table 100, and images are projected on the projectionplane 101 such as a white board.

As shown in FIG. 16, as for the conventional projector 1A, the DMD 12,the lighting unit 20, the first optical system 70, and the secondoptical system such as the curved mirror 42 are serially arranged alongin the direction perpendicular to the projection plane 101 to which aprojection image is projected. Therefore, the length of the projector 1Ain the direction perpendicular to the projection plane 101 (i.e., Xdirection) becomes longer, and thereby a greater space is required forthe projector 1A in the direction perpendicular to the projection plane101.

Typically, chairs that participants sit and desks that participants usemay be arranged in the direction perpendicular to the projection plane101 when to see images projected on the projection plane 101. Therefore,if a greater space for the projector 1A is required in the directionperpendicular to the projection plane 101, the arrangement space forchairs and the arrangement space for desks are restricted, and therebynot convenient when the projector is used.

As shown in FIG. 17, as for the conventional projector 1B, the DMD 12,the lighting unit 20, and the first optical system 70 are seriallyarranged along in a direction parallel to the projection plane 101 towhich a projection image is projected. Therefore, compared to theprojector 1A shown in FIG. 16, the length of the projector 1B in thedirection perpendicular to the projection plane 101 can be set shorter.However, as for the projector 1B of FIG. 17, the light source 61 isarranged in the direction perpendicular to the projection plane 101 andis arranged after the lighting unit 20 in the direction perpendicular tothe projection plane 101, and thereby the length of the projector 1B inthe direction perpendicular to the projection plane 101 may not beeffectively set shorter.

As for the projector 1 of an example embodiment shown in FIG. 15, theimage generator A having the image generation unit 10 and the lightingunit 20, and the projection optical system B having the first opticalunit 30 and the reflection mirror 41 are serially arranged along in adirection parallel to the projection plane 101, to which a projectionimage is projected. In such a configuration, the image generator A andthe projection optical system B are serially arranged along in adirection parallel to the Y direction in FIG. 15. Further, the lightsource unit 60 and the lighting unit 20 are serially arranged along in adirection parallel to the projection plane 101, which means the lightsource unit 60 and the lighting unit 20 are serially arranged along theZ direction in FIG. 15.

As such, as for the projector 1 according to an example embodiment, thelight source unit 60, the image generation unit 10, the lighting unit20, the first optical unit 30, and the reflection mirror 41 can bearranged in a direction parallel to the projection plane 101 such as theZ direction or Y direction in FIG. 15. As such, the light source unit60, the image generation unit 10, the lighting unit 20, the firstoptical unit 30, and the reflection mirror 41 can be arranged in adirection parallel to the projection plane 101 such as the Z directionor Y direction in FIG. 15. Therefore, the length of the projector 1 inthe direction perpendicular to the projection plane 101 (i.e., Xdirection in FIG. 15) can be set shorter than the length of theprojectors 1A and 1B shown in FIGS. 16 and 17. With such aconfiguration, the projector 1 may not cause problems when arranging aspace for chairs and desks, by which the projector 1 having a goodenough level of convenience can be devised.

Further, as shown in FIG. 14, the power source unit 80 is stacked ordisposed above the light source unit 60 to supply power to the lightsource 61 and the DMD board 11, by which the length of the projector 1in the Z direction can be set shorter.

Further, although the second optical system may be configured with thereflection mirror 41 and the curved mirror 42, but the second opticalsystem can be configured with only the curved mirror 42. Further, thereflection mirror 41 can be a plane mirror, a mirror having a positiverefractive power, and a mirror having a negative refractive power.Further, the curved mirror 42 may be a concave mirror or a convexmirror. When the curved mirror 42 is a convex mirror, the first opticalsystem 70 is configured in a way so that no intermediate image isgenerated between the first optical system 70 and the curved mirror 42.

Because the light source 61 has a lifetime for effective use, the lightsource 61 is required to be replaced with a new one periodically.Therefore, the light source unit 60 is detachably attached to a body ofthe projector 1.

FIG. 18 shows a perspective view of the projector 1 viewed from a bottomface of the projector 1, wherein the bottom face may be placed on atable. As shown in FIG. 18, the bottom face of the projector 1 includesthe base member 53 and the openably closable cover 54. The openablyclosable cover 54 includes a rotate-able member 54 a. When therotate-able member 54 a is rotated, the openably closable cover 54 isunlocked from the body of the projector 1, by which the openablyclosable cover 54 can be removed from the body of the projector 1.Further, the base member 53 includes, for example, a power-source airintake port 56 at a position next to the openably closable cover 54 inthe X direction.

Further, as shown in FIG. 18, an air-intake port 84 and the input unit88 are disposed on one Y-X plane of the outer cover 59 of the projector1. The input unit 88 is used to input image data from externalapparatuses such as personal computers.

FIG. 19 shows a perspective view of the projector 1 when the openablyclosable cover 54 is removed from the projector 1. When the openablyclosable cover 54 is removed, the light-source bracket 62 of the lightsource unit 60 is exposed, wherein the exposed side is the opposite sidethat the light source 61 is attached. The light-source bracket 62includes a knob 66, which is pivotable about the pivot center O1indicated by a dotted line in FIG. 19.

When removing the light source unit 60 from the body of the projector 1,the knob 66 is pivoted and opened by picking the knob 66, by which thelight source unit 60 can be removed from an opening of the body of theprojector 1. When attaching the light source unit 60 into the body ofthe projector 1, the light source unit 60 is inserted into the body ofthe projector 1 through the opening. When the light source unit 60 isinserted into the body of the projector 1, the connector 62 a (FIG. 4)is connected with a power-source connector in the body of the projector1, and the three light source position-setting members 64 a 1 to 64 a 3of the holder 64 (FIG. 4) engage with three light source positioningmembers 26 a 1 to 26 a 3 (FIG. 6) disposed for the lighting unit bracket26 of the lighting unit 20, by which the light source unit 60 is set ata correct position in the body of the projector 1, and the attachment ofthe light source unit 60 completes. Then, the openably closable cover 54is attached to the base member 53. As such, the knob 66 is provided forthe light source unit 60, but the pass-through area 65 shown in FIG. 19,which protrudes to the openably closable cover 54 can be used as a knob.

Further, the base member 53 is disposed with three legs 55. By rotatingthe legs 55, the protruded length of the legs 5 from the base member 53can be changed, by which the height adjustment in the Y direction of theprojector 1 can be conducted.

Further, as shown in FIG. 19, an exhaust port 85 is disposed at otherY-X plane of the outer cover 59.

FIG. 20 shows a schematic view of airflow patterns in the projector 1according to an example embodiment. FIG. 20 shows the projector 1 viewedfrom the X direction, wherein the X direction is perpendicular to theprojection plane 101. As shown in FIG. 20, the projector 1 includes theair-intake port 84 disposed its one face (left side in FIG. 20), and theexhaust port 85 disposed its other face (right side in FIG. 20). Theair-intake port 84 has an opening to intake external air into theprojector 1. The exhaust port 85 has an opening to exhaust air from theprojector 1. Further, an exhaust fan 86 is disposed at a position facingthe exhaust port 85.

When the projector 1 is viewed from the X direction, which is adirection perpendicular to the projection plane 101, a part of theexhaust port 85 and a part of the air-intake port 84 may be disposedbetween the light source unit 60 and the operation unit 83.

Further, a flow path is set between a rear face of the curved mirror 42and the outer cover 59 facing the rear face of the curved mirror 42 sothat air can flow in such space. With such a configuration, the externalair taken from the air-intake port 84 can flow through along the Z-Yplane of the mirror holder 45 of the second optical unit 40 (see FIG.12), and the rear face of the curved mirror 42 by following the mirrorholder 45 and curving of the rear face of the curved mirror 42, and thenflow to the exhaust port 85.

Further, the curved mirror 42 is a concave-shaped mirror having thepositive refractive power as above mentioned, and thereby the rear faceof the curved mirror 42 has a convex shape.

When the power source unit 80 disposed over the light source unit 60 isviewed from the Z direction in FIG. 20, the power source unit 80 can beviewed as a U-shaped configuration without the side facing the lightsource unit 60. Further, the external air taken from the air-intake port84 flows along the mirror holder 45 and the curving of the rear face ofthe curved mirror 42 to the exhaust port 85, and then flows to a spaceencircled by the power source unit 80 at three sides excluding the lightsource unit 60 side, and is then exhausted from the exhaust port 85.

As such, the part of the exhaust port 85 and the air-intake port 84 aredisposed between the light source unit 60 and the operation unit 83 whenthe projector 1 is viewed from the X direction, which is a directionperpendicular to the projection plane 101. In such a configuration, anairflow passing through a space between the light source unit 60 and theoperation unit 83 and exhausted from the exhaust port 85 can begenerated.

Further, a light source blower 95 is disposed at a position that cansuck air around the color motor 21 a (FIG. 5) that drives the colorwheel 21 in the lighting unit 20. With such a configuration, the colormotor 21 a and the light tunnel 22 can be cooled using the airflowgenerated by the light source blower 95.

The air sucked in by the light source blower 95 passes a light sourceduct 96, and then flows into a light-source air supply port 64 b (FIG.4) of the holder 64. Further, a part of the air flowing into the lightsource duct 96 flows into a space between a light source housing 97 andthe outer cover 59 from an opening 96 a formed on a face of the lightsource duct 96 opposing the outer cover 59 (FIG. 19).

The air flowing into the space between the light source housing 97 andthe outer cover 59 from the opening 96 a of the light source duct 96cools the light source housing 97 and the outer cover 59, and is thenexhausted from the exhaust port 85 using the exhaust fan 86.

Further, the air flowing to the light-source air supply port 64 b flowsinto the light source 61 to cool the light source 61, and is thenexhausted from the light-source air exhaust port 64 c disposed on thetop face of the holder 64. The air exhausted from the light-source airexhaust port 64 c is then exhausted from an opening formed on the topface of the light source housing 97 to a space encircled by the powersource unit 80. Then, the air exhausted from the light source housing 97(i.e., high-temperature air) is mixed with external air (i.e.,low-temperature air) that flows around the second optical unit 40 andthen flows into the space encircled by the power source unit 80, andthen the mixed air is exhausted from the exhaust port 85 using theexhaust fan 86.

As such, the high-temperature air exhausted from the light-source airexhaust port 64 c is mixed with the external air (i.e., low-temperatureair), and then exhausted from the exhaust port 85. Therefore, exhaustingof the high-temperature air from the exhaust port 85 can be prevented,and the temperature of air exhausted from the exhaust port 85 can bedecreased to a lower temperature. The details of mixing air exhaustedfrom the light-source air exhaust port 64 c and air taken from theair-intake port 84 will be described later.

Further, the operation unit 83 is preferably disposed on a top face ofthe projector 1 so that the user can operate the operation unit 83easily. Because the projector 1 includes the transparent glass 51 on itstop face for projecting images on the projection plane 101, theoperation unit 83 may be disposed on a position corresponding to thelight source 61 when viewing the projector 1 from the Y direction.

As such, the low-temperature airflow flowing through a space between thelight source unit 60 and the operation unit 83 from the air-intake port84 to the exhaust port 85 can cool the high-temperature air, which hasbecome high temperature when the air has cooled the light source 61, bywhich the low-temperature air and high-temperature air become a mixedair. Such mixed air is then exhausted from the exhaust port 85, andthereby the movement of high temperature air to the operation unit 83can be prevented.

With such a configuration, the temperature increase of the operationunit 83, which may be caused by the air having high temperature bycooling the light source 61, can be prevented. Further, a part of airflowing from the air-intake port 84 to the exhaust port 85 flows aroundthe second optical unit 40 and then under the operation unit 83 to coolthe operation unit 83. Therefore, the temperature increase of theoperation unit 83 can be prevented.

Further, when the exhaust fan 86 sucks in air, external air can besucked from the power-source air intake port 56 disposed on the basemember 53 (FIG. 19). A ballast board to supply power or current to thelight source 61 is disposed at a position distal of the light sourcehousing 97 in the X direction of FIG. 20. The external air sucked fromthe power-source air intake port 56 can flow through a space between thelight source housing 97 and the ballast board in the upward direction tocool the ballast board. Then, the air flows to a space encircled by thepower source unit 80, disposed over the ballast board, and is thenexhausted from the exhaust port 85 using the exhaust fan 86.

Further, a cooling unit 120 to cool the heat sink 13 of the imagegeneration unit 10 and the light-source bracket 62 of the light sourceunit 60 is disposed at the lower left side of the projector 1 as shownin FIG. 20. The cooling unit 120 includes, for example, an air-intakeblower 91, a vertical duct 92 disposed under the air-intake blower 91,and a horizontal duct 93 connected at the bottom of the vertical duct92.

The air-intake blower 91 is disposed at a lower side of the air-intakeport 84 while facing the air-intake port 84. The air-intake blower 91sucks external air from the air-intake port 84 via a side face of theair-intake blower 91 facing the air-intake port 84, and also sucks airfrom the body of the projector 1 from another side, opposite the sideface of the air-intake blower 91 facing the air-intake port 84. Suchsucked airflows in the vertical duct 92 disposed under the air-intakeblower 91. The air flowing into the vertical duct 92 flows downward, andthen flows to the horizontal duct 93 connected at the bottom of thevertical duct 92.

As shown in FIG. 20, the heat sink 13 is present in the horizontal duct93. Therefore, the heat sink 13 can be cooled by the air flowing in thehorizontal duct 93. By cooling the heat sink 13, the DMD 12 can becooled effectively and efficiently, by which high temperature of the DMD12 can be prevented.

The air flowing through the horizontal duct 93 flows into thepass-through area 65 or the opening 65 a disposed for the light-sourcebracket 62 of the light source unit 60 (FIG. 4). The air flowing intothe opening 65 a flows through a space between the openably closablecover 54 and the light-source bracket 62, and cools the openablyclosable cover 54.

Meanwhile, the air flowing into the pass-through area 65 cools thelight-source bracket 62, and then flows into a space opposite the lightexit side of the light source 61 to cool a face of a reflector so thatthe reflector of the light source 61 is cooled, in which the face of thereflector cooled by the air is a face opposite the reflection face ofthe reflector. Therefore, the air that passes through the pass-througharea 65 can take heat from both of the light-source bracket 62 and thelight source 61.

The air, which has passed near the reflector, passes through an exhaustduct 94, which is used to guide the air from the top side of thelight-source bracket 62 to the lower side of the exhaust fan 86, andthen converges into the air exhausted from the light-source air exhaustport 64 c, and then flows to the exhaust port 85, and then the air canbe exhausted from the exhaust port 85 using the exhaust fan 86.

Further, the air flowing into a space between the openably closablecover 54 and the light-source bracket 62 through the opening 65 a coolsthe openably closable cover 54, and then flows inside the projector 1,and is then exhausted from the exhaust port 85 using the exhaust fan 86.

As such, the light-source bracket 62 can be cooled by providing thepass-through area 65 for the light-source bracket 62. By coolinglight-source bracket 62, the temperature increase of the light source 61can be prevented. Therefore, the light source 61 can be cooledeffectively even if the flow rate of cooling air flowing into the lightsource 61 is decreased. If the flow rate of cooling air is decreased,the revolutions per minute (rpm) of the light source blower 95 can bereduced, by which wind noise of the light source blower 95 can besuppressed. Further, by reducing the revolutions per minute (rpm) of thelight source blower 95, the power-saving of the projector 1 can beenhanced.

A description is given of mixing of air exhausted from the light-sourceair exhaust port 64 c, which may be called as light-source exhaust air,and air taken from the air-intake port 84, which may be called aslow-temperature air The light-source exhaust air may be also referred toas hot-air exhaust, which is exhausted from the light source.

FIG. 21 shows a perspective view of a mixing duct 98 with the lightsource housing 97. The mixing duct 98 is an example of a mixing unit tomix the hot-air exhaust (or high-temperature air) and thelow-temperature air. As shown in FIG. 21, the mixing duct 98 is disposedover the light source housing 97. The mixing duct 98 has an opening ateach side in the Z direction.

FIG. 22 shows a cross-sectional view of FIG. 21. As shown in FIG. 22, alight-source exhaust duct 99 is disposed in the light source housing 97.The light-source exhaust duct 99 guides the hot-air exhaust in thevertical upward direction to send the hot-air exhaust into the mixingduct 98. Such light-source exhaust duct 99 can be used as a first flowpath.

One end (or lower end) of the light-source exhaust duct 99 is connectedto an opening of the light source housing 97, which is set just abovethe light-source air exhaust port 64 c of the holder 64, and other end(or upper end) of the light-source exhaust duct 99 is connected to anopening set on the bottom face of the mixing duct 98. The mixing duct 98is disposed in a space encircled by the power source unit 80.

FIG. 22 shows a power factor correction (PFC) main power source board 80a, and a PFC sub-power source board 80 b of the power source unit 80.Further, the operation unit 83 is disposed over the PFC main powersource board 80 a. Further, a thermo switch 182 is disposed at theexhaust fan 86 side of the PFC sub-power source board 80 b (right sidein FIG. 22). When the thermo switch 182 detects a given temperature ormore, the power voltage supply to the power source unit 80 is stopped.

The hot-air exhaust exhausted from the light-source air exhaust port 64c of the holder 64 increases its temperature when the air takes heatfrom the light source 61. As shown in FIG. 22, such hot-air exhaustrises in the light-source exhaust duct 99, and hits a upper-side face(or wall face) of the mixing duct 98 with the effect of the updraftforce of the hot-air exhaust, the suction power of the exhaust fan 86,and the wind pressure of the light source blower 95.

As shown in FIG. 22, the mixing duct 98 has openings such as an inflowport 98 a and an outflow port 98 b to arrange a second flow path. Theinflow port 98 a is disposed at the left side of the mixing duct 98 inFIG. 22, and the outflow port 98 b is disposed at the exhaust fan 86side of the mixing duct 98.

A part of the low-temperature air flowing from the air-intake port 84 toa space around the second optical unit 40 further flows into the mixingduct 98 via the inflow port 98 a, and is then mixed with the hot-airexhaust that hits the upper-side face or wall face of the mixing duct98. With such a mixing process, the hot-air exhaust decreases itstemperature, and such mixed-air (hereinafter, first mixed-air) flowstoward the exhaust fan 86. Further, the first mixed-air flows out of theoutflow port 98 b of the mixing duct 98, and is then mixed with anotherair that is taken from the air-intake port 84 between the outflow port98 b and the exhaust port 85. Such another air, which does not flow intothe second flow path, comes from the outer peripheral sides (e.g., upperside, other sides) of the mixing duct 98. Such further mixed-air(hereinafter, second mixed-air) further decreases its temperature, andthe second mixed-air is exhausted from the exhaust fan 86 to the outsideof the projector 1.

As such, the hot-air exhaust that has taken heat from the light source61 and increases its temperature (i.e., high-temperature air) can bemixed with the low-temperature air, and is then exhausted to the outsideof the projector 1, by which the temperature of the exhaust airexhausted from the exhaust port 85 can be prevented from becoming toohigh temperature.

Further, in the above described example embodiment, the mixed aircomposed of the hot-air exhaust (i.e., high-temperature air) and thelow-temperature air, mixed by the mixing duct 98, can be further mixedwith another low-temperature air at a space between the mixing duct 98and the exhaust port 85, and is then exhausted from the exhaust port 85.Therefore, compared to mixing the air exhausted from the exhaust port 85with the cool air only once, the mixed air of hot-air exhaust (i.e.,high-temperature air) and the low-temperature air mixed by the mixingduct 98 can be exhausted with a further low temperature condition.

Further, the hot-air exhaust (i.e., high-temperature air) hits theupper-side face of the mixing duct 98, by which air current of thehot-air exhaust can be disturbed. Then, the low-temperature air flowingfrom the inflow port 98 a flows into such air-current disturbed portion,by which the mixing of the hot-air exhaust (i.e., high-temperature air)and the low-temperature air can be accelerated, and the temperature ofthe hot-air exhaust (i.e., high-temperature air) can be decreasedeffectively.

Further, the inflow direction of the hot-air exhaust (i.e.,high-temperature air) into the mixing duct 98 and the inflow directionof the low-temperature air flowing in the inflow port 98 a can be setperpendicular with each other. With such a configuration, the aircurrent of the hot-air exhaust (i.e., high-temperature air) in themixing duct 98 can be disturbed, by which the mixing of the hot-airexhaust (i.e., high-temperature air) and the low-temperature air can beaccelerated.

Further, because such mixed exhaust air (i.e., first mixed air) can beexhausted from the mixing duct 98 while disturbing the air current, suchmixed exhaust air can be effectively mixed with another low-temperatureair, flowing from a space outside the mixing duct 98, at a space betweenthe exit side of the mixing duct 98 and the exhaust fan 86. The mixingof the mixed exhaust air (i.e., first mixed air) and the anotherlow-temperature air can be accelerated at a space between the mixingduct 98 and the exhaust fan 86, and thereby the temperature of theexhaust air exhausted from the exhaust port 85 can be decreasedeffectively.

If the air is exhausted from the exhaust port 85 without conducting suchmixing process, the exhausted air may have different temperature layerssuch as a warm layer (layer of mixed air) and a cool layer (air notmixed with mixed air exhausted from the mixing duct 98). By conductingthe above-described mixing process, such different temperature layerscondition may not occur.

Further, the hot-air exhaust that has taken heat from the light source61 and increased its temperature can be guided to the vertical upwarddirection using the light-source exhaust duct 99, and then can be flowedinto the mixing duct 98 using the updraft force of the hot-air exhaust.

With such a configuration, the hot-air exhaust having the hightemperature can be effectively and efficiently exhausted from the lightsource housing 97, by which the high temperature condition in the lightsource housing 97 of the light source 61 can be prevented, and a drop ofcooling efficiency of the light source 61 can be prevented.

Further, because the hot-air exhaust (i.e., high-temperature air) canflow into the mixing duct 98 using the updraft force of the hot-airexhaust, the hot-air exhaust can be exhausted from the light sourcehousing 97 even if the flow rate of air flowing to the light source 61by the light source blower 95 becomes low. Therefore, the revolutionsper minute (rpm) of the light source blower 95 can be reduced, by whichwind noise caused by the light source blower 95 can be reduced. Further,by reducing the rpm of the light source blower 95, the power-saving ofthe projector 1 can be enhanced.

Further, as shown in FIG. 22, the PFC main power source board 80 a ofthe power source unit 80 and the operation unit 83 are disposed abovethe mixing duct 98 used as the mixing unit. As such, the mixing duct 98is disposed between the power source unit 80 and the light source unit60, and the mixing duct 98 is disposed between the operation unit 83 andthe light source unit 60. With such a configuration, the hot-air exhausthaving high temperature (i.e., high-temperature air) may not hit the PFCmain power source board 80 a of the power source unit 80 and theoperation unit 83 directly, by which high temperature condition of thePFC main power source board 80 a and the operation unit 83 can beprevented. Therefore, the high temperature condition of the operationunit 83 can be prevented, and a user may not feel too-hot condition ofthe operation unit 83 when touching the operation unit 83, and theprecision of power control of the PFC main power source board 80 a canbe enhanced. If the power source unit 80 becomes the high temperaturecondition, the precision of power control may decrease due the hightemperature condition of the power source unit 80.

Further, as shown in FIG. 23, a plurality of plate members 98 c can bedisposed in the mixing duct 98. The plate member may be also referred toa fin. Each of the plurality of plate members 98 c may be disposed inparallel to the horizontal direction while setting a given interval inthe vertical direction with each other. The plate members 98 c are setat positions shifted in the horizontal direction, which is the inflowdirection of the low-temperature air. Specifically, the plate member 98c disposed at the upper position is set at a position closer to theexhaust port 85, and the plate member 98 c disposed at the lowerposition is set at a position far from the exhaust port 85. Therefore,as shown in FIG. 23, the positions of the plurality of plate members 98c becomes higher as the positions of plate members 98 c becomes closerto the closer to the exhaust port 85.

In the configurations of FIGS. 21 and 22, the layer of high temperatureair may be generated at the upper part of the mixing duct 98, in whichthe high temperature air and external air may not be effectively mixedin the mixing duct 98.

In the configuration of FIG. 23, the plurality of plate members 98 c isdisposed in the mixing duct 98. Therefore, the hot-air exhaust rising inthe mixing duct 98 hits the plate member 98 c disposed at the lowerside, by which the air current of the light-source exhaust can bedisturbed. With such a configuration, the low-temperature air flowingfrom the inflow port 98 a can be effectively mixed with the hot-airexhaust (i.e., high-temperature air), by which the temperature of thehot-air exhaust can be decreased effectively.

Further, the hot-air exhaust (i.e., high-temperature air) that hits theplate member 98 c disposed at the lower position further rises by theupdraft force of the hot-air exhaust, and moves toward the exhaust fan86, and then hits another plate member 98 c disposed at further upperposition. As such, the rising hot-air exhaust may hit the plate members98 c one by one as the hot-air exhaust rises.

With such a configuration, the air current of the hot-air exhaust (i.e.,high-temperature air) can be effectively disturbed, and the hot-airexhaust (i.e., high-temperature air) can be further mixed with thelow-temperature air.

As such, because the plate members 98 c disposed at the higher positionsare closer to the exhaust fan 86 compared to the plate members 98 cdisposed at the lower positions, the mixing of the hot-air exhaust andthe low-temperature air can be further accelerated in the mixing duct98, by which temperature of the hot-air exhaust can be effectivelydecreased in the mixing duct 98.

Further, because the air current exhausted from the mixing duct 98 isdisturbed by the plate members 98 c, such exhausted air can beeffectively mixed with another low-temperature air flowing around aspace outside the mixing duct 98, which is used as a third flow path, ata space between the exit side of the mixing duct 98 and the exhaust fan86, the temperature of the hot-air exhaust (i.e., high-temperature air)can be further decreased. With such a configuration, the temperature ofthe exhaust air exhausted from the exhaust port 85 can be furtherdecreased.

(Variant Example Embodiment)

A description is given of a variant example embodiment with reference toFIGS. 24 to 26. FIG. 24 shows a schematic perspective view of a mixingduct according to a variant example embodiment, and FIG. 25 shows across-sectional view of the mixing duct of FIG. 24. As shown in FIGS. 24and 25 as the variant example embodiment, the mixing duct 98 includes aninclining member 98 d, and the inclining member 98 d is provided withthe inflow port 98 a used as the second flow path.

In this variant example embodiment, the hot-air exhaust rises in thelight-source exhaust duct 99 used as the first flow path (FIG. 25), andflows into the mixing duct 98 while being guided by the inclining member98 d in the direction toward the exhaust fan 86. The hot-air exhaust(i.e., high-temperature air) moving along the inclining member 98 d canbe mixed with the low-temperature air flowing from the inflow port 98 a.

Further, by forming the plurality of the inflow ports 98 a on theinclining member 98 d, the air current in the mixing duct 98 can bedisturbed effectively, by which the mixing of the hot-air exhaust andthe low-temperature air in the mixing duct 98 can be furtheraccelerated, by which the temperature of the hot-air exhaust can bedecreased effectively in the mixing duct 98.

Further, because the air flow exhausted from the mixing duct 98 isalready disturbed by the air from the plurality of inflow ports 98 a,the exhaust air can be effectively mixed with the low-temperature air,flowing around a space outside the mixing duct 98, at a space betweenthe mixing duct 98 and the exhaust fan 86, by which the temperature ofthe hot-air exhaust can be further decreased. With such a configuration,the temperature of exhaust air exhausted from the exhaust port 85 can befurther decreased.

Further, in the variant example embodiment, the cross-sectional shape ofthe mixing duct 98 can be set greater as closer toward the exhaust fan86. With such a configuration, the hot-air exhaust flowing into themixing duct 98 can be effectively diffused and mixed with thelow-temperature air, flowing around a space outside the mixing duct 98,at a space between the mixing duct 98 and the exhaust fan 86, by whichthe temperature of the hot-air exhaust (i.e., high-temperature air) canbe further decreased effectively.

Further, as shown in FIG. 26, the inclining member 98 d having astep-like shape may be used. The inclining member 98 d of step-likeshape has a concave/convex shape. By forming the concave and convexportions for the inclining member 98 d, the air current of the hot-airexhaust (i.e., high-temperature air) guided by the inclining member 98 dcan be disturbed, by which the hot-air exhaust (i.e., high-temperatureair) can be effectively mixed with the low-temperature air flowing fromthe inflow port 98 a.

Further, if the inclining member 98 d is a flat member, the flare lightcorning from the light source 61 may reflect regularly at the incliningmember 98 d, and then exits from the exhaust port 85. In contrast, byforming the concave/convex shape for the inclining member 98 d, thelight coming from the light source 61 can be diffused and reflected atthe inclining member 98 d, by which the flare light may not exit fromthe exhaust port 85. Further, although the inclining member 98 d isformed as step-like shape in FIG. 26, the inclining member 98 d can beshaped in any shapes as long as the concave/convex shape is formed.

The above-described example embodiment may have following effects. Theabove-described image projection apparatus includes the light source 61,and uses light emitted from the light source 61 to project images. Theabove-described image projection apparatus includes the air-intake port84, the exhaust port 85, the ventilation unit, the first flow path, andthe second flow path. The air-intake port 84 is used to take in air intothe body of the projector 1. The exhaust port 85 is used to exhaust airfrom the body of the projector 1. The ventilation unit includes, forexample, the exhaust fan 86 to cause an airflow that flows from theair-intake port 84 to the exhaust port 85. The first flow path includes,for example, the light-source exhaust duct 99, to which the hot-airexhaust that has increased its temperature with the effect of the lightsource 61 flows in. The second flow path includes, for example, theinflow port 98 a, into which a part of the low-temperature air, takenfrom the air-intake port 84 and having a temperature lower than thehot-air exhaust flows. The above-described image projection apparatusfurther includes the mixing unit such as the mixing duct 98 that is usedto mix the hot-air exhaust flowing from the first flow path and thelow-temperature air flowing from the second flow path. The mixed airexhausted from the mixing unit converges with the air taken from theair-intake port 84, but not flowing into the second flow path, at aspace between the mixing unit and the exhaust port 85. With such aconfiguration, the mixed air exhausted from the mixing unit can befurther mixed with the air taken from the air-intake port 84 before themixed air is exhausted from the exhaust port 85. With such aconfiguration, the air can be exhausted from the exhaust port 85 whileeffectively cooling the exhaust air at a good enough level.

Further, in the above-described image projection apparatus, the inflowdirection of the hot-air exhaust (i.e., high-temperature air) taking infrom the first flow path and the inflow direction of the low-temperatureair taking in from the second flow path are set perpendicular with eachother. With such a configuration, the air current of hot-air exhaust canbe effectively disturbed, and the hot-air exhaust and thelow-temperature air can be mixed effectively can be mixed effectively inthe mixing unit.

Further, in the above-described image projection apparatus, the mixingunit has a wall face, and the hot-air exhaust (i.e., high-temperatureair) flowing from the first flow path hits the wall face of the mixingunit. Further, the low-temperature air flowing from the second flow pathflows to a space defined by the wall face and the first flow path. Withsuch a configuration, when the hot-air exhaust hits the wall face, theair current of the hot-air exhaust is disturbed, and then thelow-temperature air flows into such air current disturbed hot-airexhaust. With such a configuration, the hot-air exhaust and thelow-temperature air can be mixed effectively at the mixing unit. Assuch, the mixed air can be exhausted from the mixing unit under theair-current disturbed condition, and further, the mixed air can beeffectively mixed with the low-temperature air at a space between themixing unit and the exhaust port 85.

Further, in the above-described image projection apparatus, a pluralityof plate members 98 c are disposed in the mixing unit, in which each ofthe plate members 98 c extends in a direction parallel to a flowdirection of the low-temperature air taking in from the second flowpath, and the plurality of plate members 98 c are disposed in the mixingunit while setting a given interval between the plate members 98 c in adirection perpendicular to a flow direction of the low-temperature airtaking in from the second flow path. With such a configuration, thehot-air exhaust can hit the plate members 98 c many times, by which theair current of the hot-air exhaust in the mixing unit such as the mixingduct 98 can be effectively disturbed, and thereby the mixing of thehot-air exhaust and the low-temperature air in the mixing unit can beaccelerated. With such a configuration, the temperature of the hot-airexhaust can be decreased effectively, it can prevent that thetemperature of exhaust air exhausted from an exhaust unit such as theexhaust port 85 becomes too high temperature.

Further, because the mixed air can be exhausted from the mixing unitunder the air-current disturbed condition, the mixed air can beeffectively mixed with the low-temperature air at a space between themixing unit and the exhaust port 85.

Further, in the above-described image projection apparatus, each of theplate members 98 c are disposed in the mixing unit while shifting theposition of each of the plate members 98 c in a flow direction of thelow-temperature air taking in from the second flow path. Specifically,the plate members 98 c disposed near to the first flow path are set farfrom an exhaust unit, and the plate members 98 c disposed farther fromthe first flow path are set near to the exhaust unit. With such aconfiguration, the hot-air exhaust having high temperature can hit theplate members 98 c many times in the mixing unit such as the mixing duct98 when the hot-air exhaust flows toward the exhaust unit such as theexhaust port 85. With such a configuration, the air current of hot-airexhaust can be disturbed effectively, and the mixing of the hot-airexhaust and the low-temperature air in the mixing unit can be furtheraccelerated.

Further, in the above-described image projection apparatus, an incliningmember can be disposed in the mixing unit. The inclining member, angledwith respect to the exhaust unit, has the second flow path. With such aconfiguration, as described in the variant example embodiment, the aircurrent of the hot-air exhaust (i.e., high-temperature air) moving alongthe inclining member can be disturbed by the low-temperature air takingin from the inflow port 98 a, and the hot-air exhaust and thelow-temperature air can be mixed in the flow path. With such aconfiguration, the temperature of the hot-air exhaust can be decreasedin the mixing unit, and thereby the temperature of the exhaust airexhausted from the exhaust port 85 can be decreased.

Further, because the mixed air can be exhausted from the mixing unitunder the air-current disturbed condition, the mixed air can beeffectively mixed with the low-temperature air at a space between themixing unit and the exhaust port 85.

Further, the cross-shape of the mixing unit such as the mixing duct 98can be set greater as closer toward the exhaust port 85. With such aconfiguration, the air flowing in the mixing unit can be effectivelydiffused and then exhausted from the mixing unit. With such aconfiguration, the mixed air can be effectively mixed with thelow-temperature air at a space between the mixing unit and the exhaustport 85.

Further, in the above-described image projection apparatus, theinclining member 98 d may be formed into a step-like shape to formconcave and convex portions for the inclining member 98 d. With such aconfiguration, the air current of the hot-air exhaust (i.e.,high-temperature air) guided by the inclining member 98 d can bedisturbed effectively, by which the mixing of the hot-air exhaust andthe low-temperature air in the mixing unit can be accelerated, andthereby the temperature of hot-air exhaust can be decreased effectively.

Further, because the mixed air can be exhausted from the mixing unitunder the air-current disturbed condition, the mixed air can beeffectively mixed with the low-temperature air at a space between themixing unit and the exhaust port 85.

Further, in the above-described image projection apparatus, the mixingunit is disposed at a position between the light source unit and thepower source unit that supplies power to the light source unit. Withsuch a configuration, the hot-air exhaust having high temperature (i.e.,high-temperature air) is mixed with the low-temperature air in themixing unit, by which the temperature of the hot-air exhaust can bedecreased, and thereby the high temperature condition of the powersource unit, which may be caused by the heat of hot-air exhaust, can beprevented. Therefore, the power source unit can supply power to thelight source or the like stably.

Further, in the above-described image projection apparatus, the mixingunit is disposed at a position between the operation unit 83 that a useruses for operating the apparatus, and the light source unit 60. Withsuch a configuration, the hot-air exhaust having high temperature (i.e.,high-temperature air) is mixed with the low-temperature air in themixing unit, by which the temperature of the hot-air exhaust can bedecreased, and thereby the high temperature condition of the operationunit 83, which may be caused by the heat of hot-air exhaust, can beprevented. With such a configuration, the temperature increase of theoperation unit 83, which may be caused by the air having hightemperature by cooling the light source 61 can be prevented. Therefore,even if the operation unit 83 is disposed on the top face of theapparatus, a user can operate the operation unit 83 without feeling toomuch heat that causes the user difficult to operate the operation unit83.

In the above described example embodiments, the mixed air exhausted fromthe mixing unit can be mixed with air taken from the intake port, butnot flowing into the second flow path at a space between mixing unit andthe exhaust port. Therefore, the exhaust air can be exhausted from theexhaust port by effectively cooing the exhaust air. Numerous additionalmodifications and variations are possible in light of the aboveteachings. It is therefore to be understood that within the scope of theappended claims, the disclosure of the present invention may bepracticed otherwise than as specifically described herein. For example,elements and/or features of different examples and illustrativeembodiments may be combined each other and/or substituted for each otherwithin the scope of this disclosure and appended claims.

What is claimed is:
 1. An image projection apparatus comprising: a lightsource to emit light for projecting an image to be projected; an intakeport to take in low-temperature air into the image projection apparatus;an exhaust port to exhaust air from the image projection apparatus; aventilation unit to generate an air flow from the intake port to theexhaust port; a first flow path for hot-air exhaust having increased itstemperature by taking heat from the light source while flowing aroundthe light source; a second flow path for a part of the low-temperatureair, taken from the intake port, having a temperature lower than thehot-air exhaust; and a mixing unit to mix the hot-air exhaust flowingfrom the first flow path and the low-temperature air flowing from thesecond flow path, wherein the air mixed and exhausted from the mixingunit converges with another part of the low-temperature air taken fromthe intake port, flowing from a third flow path set outside the mixingunit, at a space between the mixing unit and the exhaust port, whereinthe mixing unit comprises a plurality of plate members each set parallelto an inflowing direction of the low-temperature air from the secondflow path, and wherein the plurality of plate members is disposed in themixing unit at predetermined intervals in a direction perpendicular tothe inflowing direction of the low-temperature air from the second flowpath.
 2. The image projection apparatus of claim 1, wherein an inflowdirection of the hot-air exhaust flowing from the first flow path and aninflow direction of the low-temperature air flowing from the second flowpath are perpendicular to each other.
 3. The image projection apparatusof claim 1, wherein the mixing unit has a wall face that the hot-airexhaust flowing from the first flow path hits, and the low-temperatureair flows from the second flow path into a space defined by the wallface and the first flow path.
 4. The image projection apparatus of claim1, wherein a position of each of the plate members is shifted in theinflowing direction of the low-temperature air from the second flowpath, wherein the plate member disposed farthest from the first flowpath is positioned closer to an exhaust unit and the plate memberdisposed closest to the first flow path is positioned far from theexhaust unit.
 5. An image projection apparatus comprising: a lightsource to emit light for projecting an image to be projected; an intakeport to take in low-temperature air into the image projection apparatus;an exhaust port to exhaust air from the image projection apparatus; aventilation unit to generate an air flow from the intake port to theexhaust port; a first flow path for hot-air exhaust having increased itstemperature by taking heat from the light source while flowing aroundthe light source; a second flow path for a part of the low-temperatureair, taken from the intake port, having a temperature lower than thehot-air exhaust; and a mixing unit to mix the hot-air exhaust flowingfrom the first flow path and the low-temperature air flowing from thesecond flow path, wherein the air mixed and exhausted from the mixingunit converges with another part of the low-temperature air taken fromthe intake port, flowing from a third flow path set outside the mixingunit, at a space between the mixing unit and the exhaust port, andwherein the mixing unit is provided with an inclining member angled withrespect to an exhaust unit, and the second flow path is formed on theinclining member.
 6. The image projection apparatus of claim 5, whereinthe inclining member has alternating concave and convex portions.
 7. Theimage projection apparatus of claim 1, further comprising a power sourceunit to supply power to the light source, wherein the mixing unit isdisposed between the light source and the power source unit.
 8. Theimage projection apparatus of claim 1, further comprising an operationunit for operating the image projection apparatus, wherein the mixingunit is disposed between the light source and the operation unit.
 9. Theimage projection apparatus of claim 5, wherein an inflow direction ofthe hot-air exhaust flowing from the first flow path and an inflowdirection of the low-temperature air flowing from the second flow pathare perpendicular to each other.
 10. The image projection apparatus ofclaim 5, wherein the mixing unit has a wall face that the hot-airexhaust flowing from the first flow path hits, and the low-temperatureair flows from the second flow path into a space defined by the wallface and the first flow path.
 11. The image projection apparatus ofclaim 5, further comprising a power source unit to supply power to thelight source, wherein the mixing unit is disposed between the lightsource and the power source unit.
 12. The image projection apparatus ofclaim 5, further comprising an operation unit for operating the imageprojection apparatus, wherein the mixing unit is disposed between thelight source and the operation unit.